Patent GB-247156-A (GB)
Title: Improvements in machines for shaping or trueing gear wheel teeth
IPC: B23F5/06
Filed: 1925-12-21
Abstract: 247,156. Aeppli, A. Feb. 6. 1925, [Convention date]. Gear-cutting. - A machine for generating toothed gears employs two cutters or grinders and is provided with two positively connected generating-systems which operate simultaneously, a cutter or grinder being associated with each system in such a way that one cutter shapes a right hand tooth flank while the other simultaneously shapes corresponding parts of a left hand tooth flank. In Fig. 1, two slides 3, 4, are provided with grinding-wheels 9, 10 respectively, and the slides are rolled round the stationary flank under the control of flexible bands 5, 6. The grinding-wheels are arranged so that each grinder works simultaneously on corresponding portions of a flank. The diameter do of the generating circle is assumed to be equal to the pitch circle diameter of the blank so that the plane of the grinding-disc is at right angles to the rolling surface. The blank 8 is held stationary and the grinding-discs are mounted on adjustable supports 16, 17. The slides 3, 4 are movable axially of the grinders along arms 18, 19 which may be rocked about the blank axis bv adjustable rods 20, 21 actuated through a sliding rod 24 from a cam 25. During a revolution of the cam 25 each grinder moves from tip to root of a tooth flank and back again. The cam may be designed so that each grinder moves with uniform speed over the tooth profile and it is shown that this condition is obtained when the angular velocity w of the radius OT during the rolling movement is given by the equation. where y is the angle described from the starting point Po. By modification of the shape of the cam 25 any particular portion of the profile may be ground beyond the theoretical requirements. for example, the tip of the tooth may be curved somewhat more sharply than the theoretical shape to allow the engagement of loaded gear-wheels without shock. The grinding discs may be smaller than those shown in Fig. 1 and in this case either the blank or the grinding discs receive a reciprocating movement axially of the blank. In a machine embodiment working on the principle indicated in Fig. 1, the blank 8 is mounted between centres on a slide 42 reciprocated by adjustable lever mechanism from a cam 44 driven 'from an electromotor 36 through belt pulleys 48 and worm gearing 49. The grinding-discs, driven by electromotors, are mounted on supports 16, 17 movable in the grinding plane on turntables 29 supported by the slides 3, 4 which move over the rocking arms 18, 19 resting on guide beds 27, 28. The holders 31, 32 of the flexible band mechanism are adjustably mounted on the slides 3, 4 and the rocking arms are actuated by thrust rods 20, 21 secured to a slide 24 which is operated by adjustable lever mechanism from the cam 25 which is also driven from the electromotor 36 through belt pulleys 38, change gears, and worm gearing 39. The blank may be rotated by a driver on a sleeve 50 carrying a dividing wheel 51, Fig. 10, which is normally held stationary by a pawl 52. On completion of a grinding operation the locking pawl is disengaged by a 53. The blank is then indexed by means of a second cam 69 acting through a rod 56 and lever mechanism on the indexing pawl 59. After the indexing movement the locking pawl is re-engaged and the indexing pawl returned by a spring 61. The shaft 53 is actuated through bevel gearing 63, 64, 65, by a bevel sector 62 on the cam 25. The grinding wheels are withdrawn clear of the blank to permit the indexing movement by rods 66 moved axially by fixed curved projections on the frame, the rods 66 being connected to the slides 16, 17 by lever mechanism. The reciprocation of the blank and the rotation of the cam 25 are continuous until the teeth are all completed whereupon the machine may be stopped by a cam on the dividing wheel acting by electrical or mechanical means on the switch of the motor 36 or on a clutch between the cam 25 and motor 36. For grinding large blanks such as those used in turbine reduction-gear the blank may be stationary and the grinders reciprocated longitudinally of the teeth. Such machines are preferably provided with two grinding-dics A, B, on each slide as shown in Fig. 12, the disc A performing the roughing and B the finishing operation. The flexible-band mechanism may be replaced by other means such as racks and pinions for obtaining the generating movements. The Specification as open to inspection under Sect. 91 (3) (a) comprises also a modification, Fig. 1 (Cancelled), in which the slides 3, 4, are actuated by a pivoted rocker 12, corresponding rotation being imparted to the blank by means of the flexible bands 5, 6. The grinding discs are also stated to be replaceable by milling-cutters or planing-tools. This subject-matter does not appear in the Specification as accepted.